This invention relates to neutron-absorbing or neutron-shielding material, and in particular to a novel process of forming such material into a tube, and the resulting tube.
In U.S. Pat. No. 4,027,377, which is assigned to the assignee of the present application and the disclosure of which is incorporated herein by reference, disclosed is the production of neutron-absorbing or shielding material comprised of a thin, rigid sheet having a neutron-absorbing material, preferably boron carbide, surrounded by aluminum plate. In forming the sheet, an ingot is first formed with a hollow interior, and a mixture of neutron-absorbing material, such as boron carbide powder, and a finely divided metal powder, such as atomized aluminum, is installed in the hollow interior of the ingot. Thereafter, the ingot is sealed, heated to a temperature below the melting point of the metal powder, and is then hot rolled to reduce its thickness a desired amount. The hot rolling causes the particles of metal powder and boron carbide to become metallurgically bonded together so that in subsequent use the material retains its neutron-absorbing properties.
A problem with the material of U.S. Pat. No. 4,027,377 is its inability to be bent and retain its neutron-absorbing capacity at the area of the bend. Consequently, the process of U.S. Pat. No. 4,751,021 was developed to provide a sheet that can be bent. However, the bend cannot be abrupt, and therefore a relatively gentle bend is the result, with the neutron-absorbing boron carbide core being offset to one side of the sheet. That patent requires precision in manufacture, and although a quite satisfactory neutron-absorbing sheet is produced, the process is expensive.